Cytoskeleton & Response to Mechanical Stress

Question 1

Cytosol

Answer 1

Inside of cell → surrounds organelles

Question 2

Cytoskeleton is a complex network of?

It extends through ____ and attaches to?

Answer 2

Complex network of interconnected filaments and tubules → extends throughout cytosol, attaches to inner surface of plasma membrane

Question 3

Cytoskeleton plays a role in:

Answer 3

1. Cell movement
2. Cell division
3. Internal organization (allows cell to assume shapes)
4. Cell signaling
5. Cell adhesion

Question 4

Major structural elements of cytoskeleton

Answer 4

1. Microtubules
2. Microfilaments
3. Intermediate fibers

Question 5

Microtubule diameter

Answer 5

25 nm (largest)

Question 6

Microfilaments diameter

Answer 6

7 nm (smallest)

Question 7

Intermediate filament diameter

Answer 7

8-13 nm

Question 8

Ways that microtubules, microfilaments and intermediate filaments/fibers are unique to each other

Answer 8

1. Size
2. Structure
3. Intracellular distribution
4. Formed by polymerization of different proteins
5. Accessory proteins

Question 9

Microtubule functions

Answer 9

1. Cellular movement (cilia, flagella)
2. Maintenance of nerves and axons
3. Spatial orientation in cytosol → govern location of organelles

Question 10

Microtubules are cylinders. Tell me about their characteristics.

Answer 10

1. Hollow
2. Straight
3. Outer diameter = 25 nm, inner diameter = 15 nm
4. Length varies

Question 11

Wall of microtubule cylinders consists of:

Answer 11

13 protofilaments arranged side-by-side, forming a hollow center

Question 12

Protofilament

Answer 12

Forms microtubule cylinder

Heterodimer of tubulin

Question 13

2 types of tubulin

Answer 13

Alpha-tubulin

Beta-tubulin

Question 14

beta-tubulin

2 functions:

Forms:

Answer 14

1. Tubulin synthesis
2. Non-covalent binding

Forms alpha-beta heterodimers

Question 15

How many tubulin isoforms in brain?

Answer 15

5 alpha, 5 beta

Question 16

Microtubule orientation

Answer 16

Radiate toward periphery → forms centrosome

Question 17

How are microtubules regulated?

Answer 17

Microtubule associated proteins (MAPs)

Question 18

Where do MAPs bind?

What is their function?

Answer 18

Regular intervals along wall of microtuble:

1. Allows interaction with other filaments
2. Regulate growth of microtubule

Question 19

2 types of MAPs in brain

Answer 19

1. Motor MAPs

2. Non-motor MAPs

Question 20

Motor MAPs

Answer 20

Use ATP to drive transport of vesicles and organelles

Question 21

Function of non-motor MAPs

Answer 21

1. Control microtubule organism in cytoplasm

2. Nervous system

Question 22

Neurites

Answer 22

Non-motor MAP in brain reinforced by microtubules

Question 23

Neurites can differentiate into?

Answer 23

1. Axons

2. Dendrites

Question 24

Microfilament composes?

Answer 24

1. Contractile fibers of muscle cells (actin)
2. Microvilli
3. Cell cortex

Question 25

Cell cortex function

Answer 25

Mechanical support of plasma membrane → responsible for cell-surface movement

Question 26

Cell cortex is a dense network of microfilaments. Tell me about it.

Answer 26

Microfilaments are attached to the inner face of plasma membrane → causes cell surface to be structurally rigid (important in cell shape)

Question 27

Actin

Answer 27

1. Extremely abundant → in virtually all cells | 2. Building block of microfilaments

Question 28

G-Actin

Answer 28

Individual actin

Question 29

F-Actin (filamentous)

Answer 29

Polymerization of G-Actin

Question 30

Actin nomenclature

Answer 30

1. G-Actin | 2. F-Actin

Question 31

2 major groups of actin

Answer 31

1. Muscle-specific | 2. Non-muscle

Question 32

Muscle-specific actin

Answer 32

apha-actin

Question 33

Non-muscle actin

Answer 33

beta-actin and gamma-actin

Question 34

Cell surface extensions

Answer 34

Extend from edge of migrating cell → aids in movement of cell

Question 35

Actin-binding protein functions

Answer 35

1. Stabilize filaments | 2. Generate force (myosin)

Question 36

Intermediate filament roles

Answer 36

1. Structure | 2. Tension-bearing

Question 37

Intermediate filament properties

Answer 37

1. Most stable 2. Least soluble 2. Scaffold (supports entire cytoskeleton)

Question 38

Intermediate filament structure differs based on?

Answer 38

Amino acid composition between tissues

Question 39

6 classes of intermediate filaments

Answer 39

``` I and II: epithelial cells III: muscle, glial, CT IV: nerve cels V: all cells VI: embryonic nervous system ```

Question 40

How is mechanical stress important in normal physiological processes?

Answer 40

1. Cell growth 2. Function 3. Differentiation 4. Apoptosis

Question 41

2 diseases in which mechanical stress is especially relevant

Answer 41

Heart and lung diseases

Question 42

Adaptation from mechanical stress occurs via changes in:

Answer 42

1. Structure 2. Metabolism 3. Gene expression

Question 43

Tensegrity structure

Answer 43

Uses tension and compression to provide support Tensegrity = tensional integrity

Question 44

What generates tension?

Answer 44

Microfilaments

Question 45

What bears compression?

Answer 45

Microtubules

Question 46

What provides elasticity?

Answer 46

Intermediate filaments

Question 47

How does cytoskeleton adapt to stress?

Answer 47

Transmits stress to rest of structure → aligns tension bearing forces with direction of stress

Question 48

Signaling response to stress

Answer 48

ECM recognizes stress → transmits signal into cell so it can adapt as needed

Question 49

3 responses to stress

Answer 49

1. Outside-in signaling 2. Regulation of nuclear access 3. Adaptation of cytoskeleton and ECM

Question 50

How is nuclear access regulated as a response to stress?

Answer 50

Alters pore size leading to nucelus

Question 51

How does membrane respond to stress?

Answer 51

Mechanically gated ion channels

Question 52

Centrosome

Answer 52

Microtubule organizing center

Question 53

Neurites → Axons regulated by?

Answer 53

Tau

Question 54

Neurites → Dendrites regulated by?

Answer 54

MAP2

Question 55

Microfilaments found in what cells?

Answer 55

Almost all eukaryotic cells

Question 56

Cell cortex is made of?

Answer 56

Dense network of microfilaments

Question 57

Proper function of non-motor MAPs in the nervous system is dependent on?

Answer 57

Neuron and non-neuron interactions